Flow control and shut-off valves have been used in industrial processing systems such as industrial refrigeration systems for over the last century, and thousands of improvements have been made in these valves and in the overall processing system since then.
The regulating or flow control valve is usually a condition responsive valve that modulates flow through the system in response to either an external or internal condition, and one form of the latter is a metering valve that modulates flow in response to upstream pressure.
In these industrial processing systems, a manually operable shut-off valve is usually positioned upstream from the metering valve, and this valve, for example, may be a bonnet type valve where the bonnet is essentially the top closure plate on the valve into which a manually operable valve stem is threaded. A valve member carried by the end of this stem engages a stationary valve seat in a valve body when the valve is in its closed position completely blocking flow through the valve. When the valve stem is unthreaded, the valve member moves away from the seat permitting flow through the shut-off valve to the regulating valve, and the shut-off valve is usually positioned in either its fully closed or fully opened position.
A strainer assembly is usually required in the flow line between the shut-off valve and the metering valve to minimize the passing of any foreign material into the metering valve and downstream into the other processing equipment associated with the system, such as refrigeration components. Heretofore, the strainer required a separate strainer body that included an inlet flange, an outlet flange, partitioned walls for the strainer seat, and a bottom cap removably attached to the strainer body by fasteners that permits the removal of the strainer for cleaning or replacement. This requirement for a strainer body and bottom cap significantly added to the cost of the processing system bearing in mind that the valves, flow lines, flow capacity, and therefore also the size of the components in these industrial processing systems are quite large. The strainer body is a metal sand casting that requires machining the inlet and outlet flanges, the strainer seats in the partition wall and the bottom plate as well as the strainer opening for the bottom plate and the bottom plate flange, all making the strainer assembly quite costly.
The shut-off valve assembly, while required to interrupt flow through the system when desired, is a major contributor to turbulent fluid flow in the system which decreases system efficiency. One reason for this is that the valve member carried by the valve stem remains in the flow stream even when in its open position.
It is a primary object of the present invention to ameliorate the problems noted above in shut-off valve assemblies.